Abstract: A floating cover (12) for a liquid storage tank (10) is made from a plurality of prefabricated sandwich panels (30). Each panel has an upper glass fibre composite layered portion (34), a honeycomb layer (36) the same size as the upper composite layered portion (34), and a lower fibre glass composite layered portion (32) that extends around the edges of the honeycomb layer by about 0.1 m. The panels are laid adjacent and abutting each other on a supporting form work, and the gaps above the extended lower layered portion (32) are filled in with sandwich sections similar to the structural layers of the sandwich panels. The upper parts of the in-fill sections overlap the upper layered portions (34) of the prefabricated panels by about 0.1 m.